The working principle of the condensing steam turbine:
The main steam of the boiler flows from the internal nozzle of the steam turbine, pushing the moving blades to move expand and work, pushing the rotor of the steam turbine rotates at high speed and drives the generator to provide power outside. Finally, the low temperature and low pressure exhaust steam flows into the condenser and is condensed into water, which is pumped through the condensate pump into the low temperature deaerator for heating and deaeration, and then sent to the boiler via the power supply. water pump to heat and pressurize it into main steam at high temperature and high pressure in the steam turbine.
The steam from the steam turbine expands from the inlet to the exhaust port, and the volume of steam per unit mass increases hundreds or even thousands of times, so that the height of the blades at eachue level must be extended. step by step. High power condensing steam turbines require a large exhaust area and the final blades must be very long.
When the exhaust steam from the steam turbine is condensed into water in the condenser, the volume suddenly decreases, so that the closed space initially filled with steam forms a vacuum, reducing the exhaust pressure of the steam turbine and makes the steam The ideal enthalpy drop increases, thereby improving the thermal efficiency of the device. Non-condensable gases (mainly air) present at the turbine exhaust are extracted by the air extractor to maintain the necessary vacuum.
Structure diagram
Detailed information:
Type of condensation The steam turbine exhaust steam pressure has a significant impact on operating economics. The main factsThe factors affecting the condenser vacuum level are the cooling water inlet temperature and the cooling rate. The first is related to the area, season, and water supply method of the power plant; the second represents the ratio between the design cooling water flow and the turbine exhaust volume.
The cooling rate is high and a high degree of vacuum can be obtained. However, increasing the cooling rate also increases the circulating water pump energy consumption and equipment investment. Generally, the cooling rate of the surface condenser is designed to be between 60 and 120. Due to the high demand for circulating water in condensing steam turbines, the water source conditions have become l one of the important conditions for choosing the site of a power plant.
Idealement, the temperature of the condensing water of the surface condenser should be the same as the temperature of the exhaust steam, and the heat removed by the cooling water is only the latent heat of vaporization of the steam exhaust. However, in actual operation, due to the resistance to exhaust flow and the existence of non-condensable gases, the temperature of the condensing water is lower than the temperature of the exhaust steam, and the difference of temperature between the two is called subcooling. Improper arrangement of cooling water pipes, excessive condensation water level during operation, and soaking of cooling water pipes will increase the degree of subcooling. Under normal circumstances, the degree of supercooling should not exceed 1 to 2°C.
Baidu Encyclopedia - Condensing steam turbine